1. Field of the Invention
The present invention relates to a coil component for voltage transformation which is used in various electronic apparatuses.
2. Background Art
A conventional coil component will be described in the following with reference to the drawings.
FIG. 10 is an exploded perspective view of a conventional coil component. FIG. 11 is a perspective view of the coil component.
In FIG. 10 and FIG. 11, a conventional coil component comprises closed magnetic circuit core 1, primary bobbin 3 and secondary bobbin 5 built into the closed magnetic core 1. And, primary bobbin 3 has primary winding 2 coiled in groove 8, and a primary winding terminal (not shown) is planted in primary bobbin 3, and one end of primary winding 2 is connected thereto. Also, secondary bobbin 5 has primary winding 4 coiled in groove 8, and low potential terminal 6 is planted in secondary bobbin 5, and one end of secondary winding 4 is connected thereto. Further, high potential terminal 7 is planted in secondary bobbin 5, and the other end of secondary winding 4 is connected to high potential terminal 7.
Closed magnetic circuit core 1 has middle magnetic leg 10 and outer magnetic leg 11 disposed on opposing plate-like back magnetic leg 9. Two back magnetic legs 9 are arranged in parallel with each other in such manner as to sandwich the middle magnetic leg 10. And, one outer magnetic leg 11 is a rectangular magnetic leg, and the other outer magnetic leg 11 is formed of two cylindrical magnetic legs. One outer magnetic leg 11 (rectangular magnetic leg) of closed magnetic circuit core 1 is combined with primary bobbin 3, and the other two outer magnetic legs 11 (cylindrical magnetic legs) are combined with secondary bobbin 5. And, middle magnetic leg 10 is not combined with anything but provided with a gap (not shown) between it and one back magnetic leg 9.
A coil component having such a configuration is used, for example, as an inverter transformer for back light of a liquid crystal monitor or the like. And, a straight-tube discharge lamp is connected to low potential terminal 6 connected to one end of secondary winding 4 and to high potential terminal 7 connected to the other end (totaling two straight-tube discharge lamps are connected to two secondary windings 4).
As the information of prior art document related to this invention, for example, Japanese Laid-open Patent 2003-22917 is commonly known.
In the above configuration, the shapes of two outer magnetic legs 11 disposed in such manner as to sandwich the middle magnetic leg 10 are different from each other, that is, one outer magnetic leg 11 is rectangular, and the other magnetic leg 11 is cylindrical. At the same time, since one outer magnetic leg 11 and the other outer magnetic leg 11 are spaced apart from each other, magnetic flux generated from one outer magnetic leg 11 is hard to equally flow to two outer magnetic legs 11 (and it is liable to become unbalanced). Accordingly, there arises a problem that it is difficult to equalize and stabilize the output voltages of two secondary windings 4 because of the structure of closed magnetic circuit core 1.